Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-27T22:49:39.169Z Has data issue: false hasContentIssue false

The Ample Cone of the Kontsevich Moduli Space

Published online by Cambridge University Press:  20 November 2018

Izzet Coskun
Affiliation:
Department of Mathematics, Statistics and Computer Science, University of Illinois at Chicago, Chicago, IL 69607, coskun@math.uic.edu
Joe Harris
Affiliation:
Department of Mathematics, Stony Brook University, Stony Brook, NY 11794, jstarr@math.sunysb.edu
Jason Starr
Affiliation:
Department of Mathematics, Harvard University, Cambridge, MA 02138, harris@math.harvard.edu
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We produce ample (resp. NEF, eventually free) divisors in the Kontsevich space ${{\overline{\mathcal{M}}}_{\text{0,}n}}\left( {{\mathbb{P}}^{r}},d \right)$ of $n$-pointed, genus 0, stable maps to ${{\mathbb{P}}^{r}}$, given such divisors in ${{\overline{\mathcal{M}}}_{\text{0,}n+d}}$ We prove that this produces all ample (resp. NEF, eventually free) divisors in ${{\overline{\mathcal{M}}}_{\text{0,}n}}\left( {{\mathbb{P}}^{r}},\,d \right)$ As a consequence, we construct a contraction of the boundary $\,\,\mathop{\bigcup }_{k=1}^{\left\lfloor {d}/{2}\; \right\rfloor }\,{{\Delta }_{k,d-k}}$ in ${{\overline{\mathcal{M}}}_{\text{0,}0}}\left( {{\mathbb{P}}^{r}},d \right)$ analogous to a contraction of the boundary $\mathop{\bigcup }_{k=3}^{\left\lfloor {n}/{2}\; \right\rfloor }\,{{\widetilde{\Delta }}_{k,n-k}}$ in ${{\overline{\mathcal{M}}}_{\text{0,}n}}$ first constructed by Keel and McKernan.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2009

References

[CHS] Coskun, I., Harris, J., and Starr, J., The effective cone of the Kontsevich moduli space. Canad. Math. Bull., to appear. http://www.math.uic.edu/˜coskun/reveff.pdf Google Scholar
[dJS] Jong, A.J. de and Starr, J., Divisor classes and the virtual canonical bundle. http://arxiv.org/abs/math/0602642 Google Scholar
[Ful] Fulton, W., Intersection Theory, Second edition. Ergebnisse der Mathematik und ihrer Grenzgebiete. 3. Folge. A Series of Modern Surveys in Mathematics. Springer-Verlag, Berlin, 1998.Google Scholar
[Ha] Hartshorne, R.,, Algebraic Geometry. Graduate Texts in Mathematics 52, Springer-Verlag, New York, 1977.Google Scholar
[Has] Hassett, B.,Moduli spaces of weighted pointed stable curves. Adv. Math. 173 (2003), no. 2, 316352.Google Scholar
[Kap] Kapranov, M. M., Veronese curves and Grothendieck-Knudsen moduli space M0,n. J. Algebraic Geom. 2 (1993), no. 2, 239262.Google Scholar
[Kaw] Kawamata, Y., Subadjunction of log canonical divisors for a subvariety of codimension 2. In: Birational Algebraic Geometry. Contemp. Math. 207, American Mathematical Society, Providence, RI, 1997, pp. 7988.Google Scholar
[KM] Keel, S. and McKernan, J., Contractible extremal rays on M0,n. Preprint, 1996. http://arxiv.org/abs/alg-geom/9607009. Google Scholar
[Pa] Pandharipande, R., Intersections of Q -divisors on Kontsevich's moduli space M0,n(P r, d) and enumerative geometry. Trans. Amer. Math. Soc. 351 (1999), 14811505.Google Scholar
[Par] Parker, A., An elementary GIT construction of the moduli space of stable maps. Ph.D. thesis, University of Texas at Austin, 2005.Google Scholar